Tomato (Lycopersicon esculentum Mill.) is one of the most economically important vegetable crops in the world. Among the major biotic constraints, virus-associated Tomato leaf curl disease (ToLCD) is a major limiting factor affecting its cultivation and yield. Different symptoms associated with disease are reported such as leaf curling, puckering of leaves, vein yellowing, stunting, excessive branching, from pale yellowing to deep yellowing, and small leaves. The genus Begomovirus is a circular single-stranded DNA virus which is exclusively being transmitted by whitefly (Bemisia tabaci) in a persistent circulative manner. Most of the begomovirus species are monopartite (having DNA-A molecule only), except few species, which are bipartite (having DNA-A and DNA-B as the genomic component). No absolute effective control measures of the disease could be developed so far, except resistance, management of insect vectors, and altering the dates of sowing to avoid peaks of insect vector population. This chapter reports an account of history, symptoms, transmission, genome organization, distribution, and management of Tomato leaf curl disease.

Cumin (Cuminum cyminum L.), is an important export-oriented seed spice crop for India. Cumin is popularly used for flavouring food, including soups, pickles and vegetables, and for herbal medicine. India is the largest producer, consumer and exporter of cumin seed with an annual production of 0.795 million tones over an area of 1.09 million hectares. During 2020-21, India exported about 0.299 million tons of cumin worth of Rs 33280 million (Anonymous, 2021). Recently, phytoplasma suspected symptoms were observed in cumin at Agricultural Research Station, Mandor, Jodhpur, Rajasthan, India from 2019. The symptoms related to phytoplasma infection were first recorded after 70-75 days of sowing in the month of January of the years 2019 to 2022. The major symptoms recorded were yellowing, phyllody, witches-broom, yellowing and deformed elongated seeds. Disease incidence was recorded as 0.25-1.0%, 0.5-1.5%, 0.5-2.5 % and 0.5-10.6% during the years 2019, 2020, 2021 and 2022, respectively using quadrate method. In 2022, among different genotypes assessed GC 4, MCU 73, MCU 105, and MCU 32 exhibited lower disease incidences ranging from 0.5% to 1.5%, while MCU 78 recorded the highest disease incidence at 10.6%. To detect the association of phytoplasma with symptomatic cumin samples, genomic DNA was extracted from four representative cumin genotypes (CuPP-MND-01 to CuPP-MND-04) and one asymptomatic cumin plant using the Qiagen DNeasy plant mini kit (Germany). The extracted DNA was amplified using nested PCR assays with universal phytoplasma detection primers for 16S rRNA gene (P1/P7 and R16F2n/R16R2) (Schneider et al., 1995; Gundersen and Lee, 1996) and secA gene specific primers (SecAfor1/SecArev3 followed by nested PCR primers SecAfor5/ SecArev2) (Hodgetts et al. 2008; Bekele et al. 2011). The amplicons of ∼1.25 kb with 16S rRNA gene and ∼600 bp with secA gene specific primers were amplified in all symptomatic cumin plant samples and positive control of brinjal little leaf. PCR amplified products from the four selected positive samples (CuPP-MND-01 to CuPP-MND-04) of 16S rRNA gene and secA gene, were sequenced from both ends. The 1,245 bp sequences were deposited in GenBank (OQ299007-10), which showed 100% sequence identity with each other and 99.4% identity with 'Candidatus Phytoplasma citri' reference strain (GenBank accession: U15442) (Rodrigues Jardim et al. 2023). The phylogenetic analysis and virtual RFLP analysis using 17 restriction enzymes of 16S rRNA gene sequences through iPhyclassifier allowed affiliating the cumin phytoplasma strains with 16SrII-C subgroup strain with a similarity coefficient of 1 to the reference pattern of 16Sr group II, subgroup C (GenBank accession: AJ293216) (Zhao et al. 2009). In addition, the phylogenetic analysis of the secA gene-based sequences (OQ305073-76) further confirmed the close association of 16SrII-C group phytoplasmas with phyllody and witches' broom disease of cumin. Earlier 16SrII-C subgroup phytoplasma has been reported from various crops and weeds in India (Rao et al. 2021). However, no phytoplasma association has been reported earlier with cumin in India and abroad. To the best of our knowledge, this is the first report on the association of 16SrII-C group phytoplasma causing phyllody, witches' broom in cumin genotypes. This report has economic and epidemiological implications and needs immediate attention to reduce export losses due to phytoplasma disease in cumin and to prevent the potential spread to other crops.

Cumin is a key export spice of India, widely used in cooking and as herbal medicine. Since 2019, phytoplasma symptoms, including yellowing, phyllody, witches’ broom, and seed elongation, have been observed in cumin crop at the Agricultural Research Station in Mandor, and farmers field of Jodhpur, Barmer and Nagaur districts of Rajasthan. Symptoms appeared 7075 days after sowing, with disease incidence increasing from 0.25% to 10.6% in 2022. Screening of 80 cumin genotypes, GC 4, MCU 73, MCU 105, and MCU 32 showed low disease incidence (0.5-1.5%), while MCU 78 had the highest incidence (10.6%). Phytoplasma presence was confirmed in 80 cumin symptomatic germplasm accessions by employing phytoplasma specific primers. Pairwise sequence identity and phylogeny of 16S rRNA gene sequences of CuPP-Jod strains in the study indicated the presence of ‘Candidatus Phytoplasma citri’ (16SrII-C subgroup). Chickpea, lentil and weeds growing in and nearby cumin fields were also presenting phytoplasma symptoms and were also analysed for phytoplasma presence. Phylogenetic and virtual RFLP analysis of 16S rRNA gene sequences confirmed the identity of cumin and chickpea phytoplasmas as ‘Ca. P. citri’.

Mungbean [Vigna radiata (L.) R. Wilczek] is an important edible legume grown in Asia, particularly in the Indian subcontinent. A field experiment was conducted for the integrated management of leaf spot and root rot caused by Cercospora canescene and Macrophomina phaseolina (Tassi) Goid respectively at Agricultural Research Station Mandor, Jodhpur, Rajasthan. For the integrated management of the diseases, ten treatments comprising of seed treatment and foliar application of various fungicides and biocontrol agents in three replications were used in randomized block design. Among the tested treatments against leaf spot, blight and root rot, seed treatment with T. viride @ 4 g/kg + soil application of T. viride @ 2.5 kg/ha enriched in 100 kg FYM + Neem cake @ 250 kg/ha + spray of myclobutanil @ 1 g/l the leaf spot (2.6%) and root rot (3.6%) decreased by 79–84 and 72–79% respectively and found at par with seed treatment with Trichoderma viride + Pseudomonas fluorescens @ 10 g/kg + soil application of P. fluorescens @ 2.5 kg/ha in 100 kg of FYM + spray Pyraclostrobin 133 G/l + Epoxiconazole 50 G/l SE @ 1.5 ml/l which resulted in the minimum disease incidence of root rot (4.5%), disease severity of leaf spot (2.8%) and highest yield of mungbean (1019 kg/ha).